Really man, there's a couple key things here:
1. Don't worry too much about it and just move on. You're 14 man, and anyone (especially round these parts) who says they didn't act awkward at that age is just lying. It's an awkward age. Just learn from your mistakes (and yea you did make a mistake) and react differently next time.
2. On a related note - move on. It really doesn't sound like this girl is worth your time anyways. And if you like this girl like you claim, I know it's easier said than done, but she ain't worth your time and you're better off. Trust me, I know that mindset can be hard - I've been trying to talk to the same girl for 5 months now. She always acts interested when she's around me (we work together), but when I try to call her to make something happen, I can't get ahold of her and never hear back. She always has her reasons why, and always has emphasis on saying that she's interested in hanging out, but it's obvious she's not. I know she really isn't worth my time, but I keep getting myself caught up anyways.
It's easier said than done, but this girl isn't worth your time if she's going to act like that towards you.
I guess I was even in a similar situation here the other day. I went out after work to grab a couple beers, and while I was out I ran into a girl that I work with at my other job. She's a bartender, and was out with one of her regulars. I saw her, we had a couple drinks, and then the 3 of us ended up going over to another place. Her friend left us on our own, and we were talking and such, and some dude came over to start hitting on her. We both thought this guy was sent by her friend, so we let him kick it for a bit, but when it became obvious she wasn't interested, I started backing him out of our space. Later on in the night, when we began to mingle with a bunch of other people, another dude started hitting on her, and while he was, one of the girls asked me "Is that your girlfriend?!", to which I said "Oh no we're not together".
We aren't together, and I've only hung out with her a couple times. I wasn't even really trying to hit on her, so I didn't really feel any threat, so I just let her have her fun talking to all the drunken bar guys. Didn't really bother me too much.
I wasn't sure if I was "supposed" to act out or not, but because I'm not particularly trying to whoo her, as well as not feeling any attraction from her, I just didn't particularly care and the situation wasn't awkward for me, so I just sat back and didn't really say anything.